Emerging evidence implicates posttraumatic stress disorder (PTSD) as a risk factor for medical morbidity including cardiovascular conditions. African Americans have higher rates of HTN and its consequences than Americans of European ancestry. Clinical and epidemiological studies that indicate a relationship between PTSD and HTN had substantial minority participation while the subjects of a large study that failed to find this relationship were predominately white. An absence of the normal "dip" of blood pressure (BP) at night is an important risk factor for HTN and for its end-organ complications. "Non-dipping" of nocturnal BP is common among people of African descent. A study of African American adolescents found an association between "non-dipping" and exposure to violence. Research findings implicate sympathetic nervous system (SNS) activity and alpha1-adrenergic mechanisms in non-dipping of nocturnal BP and in the sleep disturbance of PTSD. Our pilot data supports a relationship between PTSD and nocturnal BP non-dipping in a group of young adult African Americans. The goal for the present study is to more definitively evaluate this relationship and characterize the contributions of sleep factors, nocturnal SNS activity, chronic stress, coping responses, and behavioral/life style factors. This will be accomplished by recruiting healthy young adult African American men and women. The initial study phase will screen for trauma exposure and PTSD symptoms. From the initial phase participants we will select a group for laboratory procedures that is balanced for the presence or absence of lifetime PTSD. The procedures include polysomnographic evaluation, and 2, 24 hour blood pressure, heart rate, and activity monitoring recordings conducted a week apart. As the relationship between BP non-dipping and PTSD, and the role of contributing factors are elucidated, we plan to develop preventive interventions. PUBLIC HEALTH RELEVANCE: Trauma exposure is common among urban residing African Americans who also disproportionately experience hypertension and consequent cardiovascular morbidity and mortality. This study will elucidate a mechanism by which trauma exposure through PTSD effects cardiovascular morbidity that has preventive implications.